1. Field of the Invention
The present invention relates generally to hypodermic syringes and phlebotomy apparatus and more particularly to improvements in a protective cover for the hypodermic needle of disposable hypodermic syringes and phlebotomy apparatus that advantageously prevent inadvertent needle sticks or punctures, both before and after use of the syringe or apparatus.
2. Description of the Prior Art
Infectious diseases can be transmitted to medical personnel and others by way of inadvertent needle sticks or punctures with an infected needle of a hypodermic syringe or phlebotomy apparatus. Cases have been reported in which human HIV (AIDS) infection and other infectious diseases have been transmitted by accidental or inadvertent needle sticks. A number of devices have been developed for the purpose of preventing such needle sticks.
One type of prior art device in common use employs a protective sheath external to the needle which is retractable to permit insertion of the needle into the body of the patient and is then slidable back over the needle past the needle point as, or after, the needle is withdrawn from the body. In some of this type of prior art protective device, a spring or axially resilient sheath is used to extend the sheath over the needle point upon withdrawal of the needle. Several of these prior art devices use a collapsible sheath formed by a plurality of resilient arms surrounding the needle and a needle cup that encloses the needle tip and prevents inadvertent needle sticks. An offset needle opening is provided in the end of the needle cup. The arms are bowable or bendable outwardly away from the needle axis and permit the needle to be guided through the offset opening for use. After use, the arms are movable inwardly toward the needle axis with or without a biasing means to again enclose the needle point within the needle cup. One example of such prior art devices is described in my U.S. Pat. No. 5,256,152.
Another example of such prior art devices is disclosed in U.S. Pat. Nos. 5,538,508 and 5,746,718 issued to Steyn, the entire subject matter of which is incorporated herein by reference. In a commercial embodiment of the Steyn safety needle device, very similar to the embodiment shown in FIGS. 1 and 2 of the Steyn patents, the needle cup is a molded polymeric end cap with an offset needle opening. The collapsible sheath is formed from a length of an extruded flexible polymeric tube with four reinforcing ribs projecting radially from the circumference of the extruded tube and equi-angularly spaced at 90° about the tube circumference. As used herein, the term “rib” or “ribs” is used to describe the longitudinally extending projection(s) from the outer circumference of the tubular member. Except for circumferential portions at the proximal and distal ends of the sheath, two opposing walls of the extruded tube between the ribs are cut out to form two flexible opposing arms, each arm having an extruded rib extending along each of its two edges. One end of the extruded tube is stretched over the needle cup and the other end is stretched over the needle support base. Notches are provided on the inside of the arms midway between the ends of the sheath which are intended to cause the arms to bow outwardly when the tubular member is axially compressed. As the two aims bow outwardly to their maximum extent, they also fold rearwardly toward the syringe barrel so that the user can manually grasp and hold the arms against the syringe barrel when administering an injection.
Although this commercial embodiment of the Steyn safety needle device is operable for its intended purpose, it has several shortcomings that can be eliminated by the improvements disclosed herein according to the present invention. In particular, those shortcomings include: (1) the flexible arms do not reliably flex outwardly when the needle is deployed, but frequently flex inwardly; (2) because of excessive lateral movement of the needle inside the needle cup, the needle point may miss the needle opening and strike the inside face of the end of the needle cup requiring repeated attempts to align the needle with the opening; (3) the user must grasp the needle cup with the fingers of one hand and urge it proximally toward the needle support thereby placing the user's fingers in very close proximity to the needle point and shaft, which could easily cause an inadvertent needle stick and/or contamination of the needle point and shaft; (4) the arms flex outwardly and rearwardly alongside the barrel of the syringe so that the user has only one hand free (one hand is holding the needle cup) to both hold the syringe and grip at least one arm and press it against the surface of the syringe barrel to keep the needle exposed for use, an extremely awkward maneuver; and (5) the device has no means for disabling itself after use to prevent its accidental reuse.
Furthermore, one of the primary shortcomings of many the prior art devices which use protective sheaths of the foregoing type is that during at least some of the period of time between the preparation of the hypodermic syringe for an injection, or the phlebotomy apparatus for entering a vein, and the discarding of the used needle, inadvertent needle sticks of persons other than the patient are still possible.
It would be desirable, therefore, to provide a safety hypodermic needle for use with a disposable hypodermic syringe, as well as for use with catheter needles and other types of body-penetrating hypodermic needles, that overcomes the foregoing limitations and shortcomings of the commercial embodiment of the Steyn safety needle device as well as other prior art devices, has a minimum number of parts, is economical to manufacture and is easy and convenient to use. The present invention overcomes the aforementioned limitations of the commercial embodiment of the Steyn safety needle device and provides still further improvements over those other prior art safety devices for hypodermic needles as will be described in detail in the following specification.